1. Field of the Invention
The invention relates to a method of manufacturing a LED lamp.
2. Description of the Related Art
Conventionally, a method, in which a LED chip is sealed by pressing a plate glass softened by heat against a substrate having the LED chip thereon using a forming die, is broadly used as a method of sealing a LED chip with glass. A LED lamp sealed with glass by such a method is disclosed in WO 2004/082036 and JP 2008-124153. In addition, JP 2008-49841 discloses a method in which a concave portion for covering a LED chip is provided in a sealing glass in order to prevent the sealing glass from contacting with the LED chip, the LED chip is then covered by the sealing glass and a resin is injected between the LED chip and a forming surface of the concave portion.
According to the method of WO 2004/082036 and JP 2008-124153, it is necessary to seal the LED chip after softening the sealing glass by heating at a temperature much exceeding a yielding point and near softening point or higher, in light of the production tact required for a sealing process of the LED chip. However, the sealing glass softened by heating to the softening point or more adheres to not only a substrate but also to a forming die. Thus, it is considered that the adhesion of the sealing glass is prevented by roughening a surface of a die used for the sealing glass and decreasing a contact area of the sealing glass and the forming die. However, roughening the surface as described above is not preferable since surface accuracy of the LED lamp is reduced and light availability of the LED chip decreases. When the sealing glass is heated at a temperature lower than the softening temperature in order to avoid the above problem, the sealing glass is not sufficiently softened and an excessive force is then applied to the LED chip when the sealing glass is pressed against the substrate. This caused breakage or misalignment of the LED chip.
On the other hand, in the method of the JP 2008-49841, the LED chip is located in the concave portion of the sealing glass and is enclosed by a resin. The resin is not preferable since it is denatured and yellowed due to light or heat of the LED chip.
Therefore, one object of the invention is to provide a method of manufacturing a LED lamp in which misalignment or breakage of a LED chip is prevented. In addition, another object of the invention is to provide a method of manufacturing a LED lamp in which adhesion of a sealing glass to a forming die is prevented.